SC-45 System Time Synchronization

Baselines

Guidance

Time synchronization of system clocks is essential for the correct execution of many system services, including identification and authentication processes that involve certificates and time-of-day restrictions as part of access control. Denial of service or failure to deny expired credentials may result without properly synchronized clocks within and between systems and system components. Time is commonly expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC. The granularity of time measurements refers to the degree of synchronization between system clocks and reference clocks, such as clocks synchronizing within hundreds of milliseconds or tens of milliseconds. Organizations may define different time granularities for system components. Time service can be critical to other security capabilities—such as access control and identification and authentication—depending on the nature of the mechanisms used to support the capabilities.

References 1

• IETF 5905 Internet Engineering Task Force (IETF), Request for Comments: 5905, *Network Time Protocol Version 4: Protocol and Algorithms Specification* , June 2010.

Control Enhancements 2

• SC-45(01) Synchronization with Authoritative Time Source L M H P
• SC-45(02) Secondary Authoritative Time Source L M H P

Related controls 4

• AC-03 Access Enforcement L M H P
• AU-08 Time Stamps L M H P
• IA-02 Identification and Authentication (Organizational Users) L M H P
• IA-08 Identification and Authentication (Non-organizational Users) L M H P